This invention relates to an improved catheter, more particularly a balloon catheter for use in angioplasty. This invention is even more particularly adapted for use as a balloon dilatation catheter in percutaneous transluminal coronary angioplasty (PTCA). A PTCA procedure is used to dilate the stenosed region of a diseased coronary blood vessel. In a typical PTCA procedure, a guide catheter is introduced in a peripheral artery, such as the femoral artery, and advanced through the aorta until the distal end of the guide catheter is engaged with the coronary ostium for the coronary artery to be treated. Next a balloon dilatation catheter is introduced over a guidewire which has been introduced through the guide catheter. The guidewire is advanced past the distal end of the guide catheter within the lumen of the diseased vessel and manipulated across the region of the stenosis. The balloon dilatation catheter is then advanced past the distal end of the guide catheter over the guidewire until the balloon is positioned across the stenotic lesion. The balloon is inflated by supplying a fluid under pressure to the balloon through an inflation lumen in the catheter. Inflating the balloon stretches the diseased artery to reestablish acceptable blood flow through the artery.
A typical over the wire balloon dilatation catheter has two lumens extending through substantially the entire length of the catheter. One lumen is used to pass the guidewire through the catheter and extends from a proximal guidewire port to a distal guidewire port located distal of the balloon. The other lumen is used to inflate and deflate the balloon and extends from a proximal inflation port adjacent to the proximal end of the catheter to a distal inflation port which is in communication with the balloon cavity.
A typical rapid exchange balloon dilatation catheter has a single inflation lumen extending from the proximal end of the catheter to the distal inflation port which is in communication with the balloon cavity. The guidewire lumen extends through only the most distal portion of the catheter from a proximal guidewire port, which is proximal of the balloon but distal to the proximal end of the catheter, to a distal guidewire port in the distal end of the catheter. This configuration facilitates the maintenance of the location of the guidewire across the stenosis during catheter exchange.
A typical fixed-wire balloon dilatation catheter has a single lumen shaft that extends from the proximal end of the catheter to the proximal end of the balloon. A wire is fixed in the catheter and extends past the distal end of the balloon which is connected thereto. The fixed-wire acts as the guidewire to steer the catheter so that a separate guidewire is not needed.
In order for a balloon dilatation catheter optimally to perform its function in an angioplasty procedure, the catheter should have a small profile, a flexible distal portion and a stiff proximal portion. The small profile allows the catheter to be inserted into small arteries. A flexible distal portion allows that part of the catheter to pass through the tortuous, tight curvatures of the vasculature. In addition, a stiff proximal portion gives the catheter "pushability", i.e. transmission of longitudinal force along the catheter, so a physician can push the catheter through the vascular system and the stenosis. Finally the transition between the stiff proximal portion and the flexible distal portion should be smooth and should avoid areas of high stress concentration.
Balloon dilatation catheters currently on the market attempt to achieve these goals with varying degrees of success. However, none has heretofore provided such an optimum combination of features.
Therefore it would be desirable to provide a balloon dilatation catheter that has a small profile.
It would also be desirable to provide a balloon dilatation catheter having a flexible distal portion.
It would be further desirable to provide a balloon dilatation catheter having a stiff proximal portion.
It would be yet further desirable to provide a balloon dilatation catheter that has a smooth transition from a stiff proximal portion to a flexible distal portion which avoids areas of high stress concentration.